ELSA LANCOM Business LC-4X00, Manual

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Operating modes and functions
ELSA LANCOM Business
77
Network mask assignment
The network mask is assigned in the same way as the address. If a network mask is
entered in the DHCP module, this mask is used for the assignment. Otherwise, the
network mask from the TCP/IP module is used (same sequence as for address
assignment).
Broadcast address assignment
Normally, an address yielded from the valid IP addresses and the network mask is used
for broadcast packets in the local network. In special cases, however (e.g. when using
subnetworks for some of the workstation computers), it may be necessary to use a
different broadcast address. In this case, the broadcast address to be used is entered in
the DHCP module.
The default setting for the broadcast address should be changed by experienced network
specialists only. Incorrect configuration of this section can result in the undesired
establishment of connections subject to connect charges!
DNS and NBNS assignment
This assignment is based on the associated entries in the 'TCP-IP-module'.
If no server is specified in the relevant fields, the router passes its own IP address as a
DNS address. This address is determined as described under 'IP address assignment'.
The router then uses DNS-forwarding (also see 'DNS-forwarding'), to resolve DNS or
NBNS requests from the host.
Default gateway assignment
The router always assigns the requesting computer its own IP address as a gateway
address.
If necessary, this assignment can be overwritten with the settings on the workstation
computer.
Period of validity for an assignment
The addresses assigned to the computer are valid only for a limited period of time. Once
this period of validity has expired, the computer can no longer use these addresses. In
order for the computer to keep from constantly losing its addresses (above all its IP
address), it applies for an extension ahead of time that it is generally sure to be granted.
The computer loses its address only if it is switched off when the period of validity
expires.
For each request, a host can ask for a specific period of validity. However, a DHCP server
can also assign the host a period of validity that differs from what it requested. The
DHCP module provides two settings for influencing the period of validity:
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Maximum lease time in minutes